Vacuum collar for roofing kettles and the like

ABSTRACT

ROOFING KETTLES OR THE LIKE, FOR HEATING MASSES OF BITUMINOUS MATERIAL, PROVIDED WITH MEANS FOR REDUCING THE SMOKE, FUMES AND VAPORS GIVEN OFF IN OPERATION ARE DISCLOSED, WHICH MEANS COMPRISE VARIOUS EMBODIMENTS OF THE INVENTION. EMBODIMENTS OF THE INVENTION SUITABLE FOR RETROFITTING EXISTING KETTLES, AS WELL AS THE EMBODIMENT OF THE INVENTION IN KETTLES AS ORGINALLY BULT IN VARIOUS FORMS ARE DESCRIBED.

Feb. 27, 1973 E. A. BUSSE ETAL 3,718,131

VACUUM COLLAR FOR ROOFING KET'ILEIS AND THE LIKE Filed Feb. '7, 1972 3 Sneets-Sheet 1 Feb. 27, 1973 E. A. BUSSE ETAL 3,718,131

VACUUM COLLAR FOR ROOFING KETTLES AND THE LIKE Filed Feb. 7, 1972 3 Sheets-Sneet 2 FIG. 4

33 f fKN/f 32 C 49 Feb. 27, 1973 E. A. BUSSE ETAL 3,718,131

VACUUM COLLAR FOR ROOFING KETTLES AND THE LIKE Filed Feb. 7, 1972 3 Sheets-Sheet 3 53 I W 56 .L

i'=lq United States Patent 3,718,131 VACUUM COLLAR FOR ROOFING KETTLES AND THE LIKE Ewald A. Busse, 2302 Flores St., San Mateo, Calif.

94403, and Glen W. Raker, 2648 Graceland Ave., San

Carlos, Calif. 94062 Filed Feb. 7, 1972, Ser. No. 224,155 Int. Cl. E01c 19/45; F24h 1/00 U.S. Cl. 126-3435 A Claims ABSTRACT OF THE DISCLOSURE Roofing kettles or the like, for heating masses of bituminous material, provided with means for reducing the smoke, fumes and vapors given olf in operation are disclosed, which means comprise various embodiments of the invention. Embodiments of the invention suitable for retrofitting existing kettles, as well as the embodiment of the invention in kettles as originally built in various forms are described.

BACKCiROUND OF THE INVENTION This invention relates to the reduction of the smoke, vapor and fumes given oif in the normal operation of kettles for heating bituminous materials and more particularly to the provision of means in such kettles for drawing off such smoke, vapor and fumes and subjecting them to substantially complete combustion within the heating means of the kettle itself.

There are a number of processes such as the roofing of buildings and the construction or repair of highways in which solid bituminous material is heated to liquify it for application and subsequent solidification over a desired area. The heating of the bituminous material is conventionally carried out in portable kettles comprising a receptacle, usually mounted on wheels, provided with a removable or hinged cover and appropriate heating tubes or pipes. The heating means usually comprises a torch supplied with liquid or gaseous fuel under pressure directed into one end of the heating tubes or pipes with the products of combustion existing from the other end of the heating tubes to the atmosphere. In a properly designed kettle, the torch and heating tubes thereof are designed to provide complete combustion of the liquid or gaseous fuel with appropriate heat transfer to the bituminous material in the kettle to liquify such bituminous material. Thus, the combustion of the gaseous fuel used in heating the kettle does not tend to produce undesirable fumes and vapors in the atmosphere.

However, bituminous materials contain a variety of volatiles which are given off as smoke and vapors when such materials are melted under the influence of heat. Such smoke and vapors are combustible, usually have an obnoxious odor and generally tend to pollute the atmosphere. A number of devices are currently in use for the purpose of reducing such atmospheric pollution, all of which comprise a vent pipe or smoke stack through the cover of the kettle and in which are located auxiliary burners supplied with liquid or gaseous fuel under pressure. Thus, the smoke and fumes given off by the bituminous material in the kettle are drawn through the vent or smoke stack where they are subjected to combustion in the flame of the auxiliary burners together with the fuel. This is obviously a wasteful means of solving the problem since the auxiliary burners must be operated at a sufliciently high level to create a draft that will prevent combustion from occurring within the kettle and at the same time insure complete combustion of the smoke and vapors drawn out of the kettle. The heat produced in such combustion is dumped into the atmosphere without serving any other useful purpose than the combustion itself.

It has previously been suggested that the smoke and fumes given off by the bituminous material be drawn into the heating system of the kettle for combustion, either at the exhaust end of the heating system, as shown in US. Pat. 3,220,403 for example, or at an intermediate point in the system where the combustion of such smoke and fumes can contribute to the heating of the kettle, as shown in US. Pat. 3,046,977. However, these prior art devices have at least three major disadvantages. In the first place, the complete combustion of the smoke and fumes drawn from the kettle is highly unlikely at an intermediate point in the heating system of such kettle and almost an impossibility at the exhaust end of such heating system. In the second place, if combustion of such smoke and fumes does occur then the probability of such combustion propagating through the vent means and into the kettle itself (usually called a blow-back) is quite high due to the fact that the velocity of the gases involved decreases as the gases move through the heating system becoming lowest at the exhaust end of the system. Finally, it is often necessary to reduce the level of operation of the heating system after the kettle and bituminous material therein has reached the desired temperature and no bituminous material is being taken from or added to that in the kettle. Under such conditions, usually referred to as idling, the production of smoke and fumes from the liquified bituminous material remains relatively constant, but the possibility of combustion thereof in the heating system is reduced and the probability of a blow-back is increased.

It is an object of this invention to provide means for drawing off the smoke and fumes given off by bituminous material when heated and feeding such fumes directly into the heating flame for substantially complete combustion with reduced danger of a blow-back occurring.

It is a further object of this invention to provide such a means which will operate satisfactorily under idling conditions.

It is another object of this invention to provide such a means which can be readily applied either to existing kettles or in the construction of new kettles.

It is a further object of this invention to provide such a means which is inexpensive, tends to increase the efficiency of the kettle and tends to extend the life of the heating system of the kettle.

SUMMARY OF THE INVENTION According to this invention, a roofing kettle or the like for heating masses of bituminous material comprises a receptacle for containing such material with a removable cover spaced from the surface of such material, a heating tube of given internal dimensions extending adjacent the bottom of the receptacle with both ends extending into communication with the atmosphere, a torch unit adapted to direct a flame into one end of heating tube to communicate the desired heat to the material with the products of combustion of the flame exiting the other end of the heating tube, and is provided with a tubular member received in the heating tube at such one end thereof, which tubular member has one end flared outwardly to provide internal dimensions substantially equivalent to the internal dimensions of the heating tube with the remainder of the tubular member having smaller external dimensions than the internal dimensions of the heating tube to form a substantially annular volume therebetween open to the interior of the heating tube at the free end of the tubular member and a vent pipe communicating between such annular volume and the space between the surface of the material in the receptacle and the cover of the receptacle.

3 BRIEF DESCRIPTION OF THE DRAWING The foregoing and other objects and features of this invention will be more fully apparent from the following detailed description when read in conjunction with the drawing wherein:

FIG. 1 is a simplified plan view of an empty roofing kettle or the like for heating bituminous material according to one embodiment of this invention with portions broken away to show the heating tube;

FIG. 2 is a cross-sectional view taken along lines 2--2 of FIG. 1, but including a representation of liquid bituminous material in the kettle;

FIG. 3 is an exploded view in perspective of a three burner torch, a vacuum collar according to the embodiment of the invention shown in FIGS. 1 and 2, and an end portion of the heating pipe, including a fragment of an end wall of a kettle;

FIG. 4 is an enlarged cross-sectional view of a one burner torch and a vacuum collar according to another embodiment of this invention as well as a fragment of the end of the heating tube and the adjacent wall portion of a kettle;

FIG. 5 is a cross-sectional view taken along lines 5--5 of FIG. 4;

FIG. 6 is a plan view of an empty roofing kettle or the like of difierent design from that shown in FIG. 1, including an embodiment of this invention similar to that shown in FIG. 3;

FIG. 7 is a cross-sectional view taken along lines 77 in FIG. 6;

FIG. 8 is an enlarged fragmentary cross-sectional view of the vacuum collar according to the embodiment of this invention shown in FIGS. 6 and 7; and

FIG. 9 is a fragmentary cross-sectional view of a kettle, including an embodiment of this invention similar to that shown in FIG. 4.

DETAILED DESCRIPTION Referring to FIG. 1 a simplified plan view of one type of roofing kettle 10 currently in use for heating bituminous material is shown. Such roofing kettle 10 comprises a receptacle for the bituminous material which is a simple rectangular box consisting of side walls 11, end walls 12 and bottom wall 13 assembled in liquid tight relation. A suitable outlet is provided through one of the walls adjacent the bottom to enable the liquified bituminous material to be drawn off as needed. As shown in FIGS. 1 and 2 a simple spigot 14 communicates with an opening through one of the end walls 12 to provide an outlet for liquified bituminous material, however, it will be understood that any type of outlet may be used for drawing ofif the liquified bituminous material as desired.

As shown in FIGS. 1 and 2, the open top of the receptacle formed by side walls 11, end walls 12 and bottom wall 13 is closed by a two-part removable cover 15. One part 16 supports a burner Well 17 and heating tubes 18 within the receptacle from the open top thereof as will be more fully described hereinafter. The other part 19 of the removable cover is mounted on the first part 16 by means of hinges 20 in order to facilitate the addition of solid bituminous material as the liquified bituminous material is drawn ofl for utilization.

As shown in FIGS. 1 and 2 the burner well 17 comprises a smaller hollow box having a shape similar to that of the receptacle and consisting of side walls 21, end walls 22 and bottom wall 23 assembled in liquid tight relation. The open end of the burner well 17 is mounted on the part 16 of the removable cover in registry with an opening therethrough. Thus, when the removable cover is placed on the receptacle, the burner well 17 will project downwardly from the cover into the receptacle with one of its end walls 22 adjacent an end Wall 12 of the receptacle.

As shown in FIGS. 1 and 2 the heating tube 13 comprises a first portion 24 mounted on the other end wall 22 of the burner Well 17 and communicating with the burner well 17 through an opening in such end wall 22 adjacent the bottom wall 23. A portion 24 of the heating tube 18 extends along the bottom Wall 13 of the receptacle toward the opposite end wall 12 where it joins a transverse portion 25 of the heating tube :18. The ends of the transverse portion 25 of the heating tube communicate with return portions 26 of the heating tube 18 which extend along the bottom wall 13 of the receptacle toward the end wall 12 of the receptacle adjacent the burner well 17 and such return portions 26 terminate in upwardly extending portions 27 which are rigidly mounted on the part 16 of the removable cover 15 and extend through openings therein into communication with the atmosphere.

As shown in FIGS. 1 and 2 a single burner torch 30 is inserted into the burner well 17 and directed into portion 24 of the heating tube 18 through the opening in the end wall 22 of the burner well 17. The torch 30 is supplied with liquid or gaseous fuel under pressure through an appropriate feed line 31 and includes an appropriate jet 32 and burner shell 33. It will be understood that the flame from the torch 30 enters the portion 24 of the heating tube 18 with substantial velocity due to the combustion and consequent expansion of gases in the flame. The flame and hot gases from the torch 30 proceed along the portion 24 of the heating tube to the transverse portion 25 thereof where they are conducted to the return portions 26 of the heating tube and are finally expelled into the atmosphere through the portions 27 of the heating tube. As the flame and hot gases pass through the heating tube 18, they communicate heat to the bituminous material represeted in its liquified form 34 in FIG. 2.

It will be understood that bituminous materials having a wide variety of compositions may be heated in kettles of the type described above in order to liquify them for subsequent utilization. The composition of the bituminous material in any instance depends on the purpose for which such bituminous material is to be used, but in every case the composition of the bituminous material includes a large percentage of volatiles which are given Off when the bituminous material is liquified by heating it. Such volatiles control characteristics of the bituminous material such as its melting point and physical attributes at various temperatures. Thus, such volatiles are essential to the use of bituminous materials in their various applications, however, such volatiles characteristically have an obnoxious odor and a tendency to pollute the atmosphere as given off in the process of liquifying the bituminous material by the application of heat thereto. One of the purposes of the removable cover 15 is to inhibit the escape of such volatiles to the atmosphere. However, it is impractical to make the removable cover 15 in such a way as to provide a hermetic seal with the receptacle and thus a substantial amount of such vapor continuously escapes to the atmosphere in operation. Furthermore, it is necessary to open the hinged portion 19 of the cover 15 periodically in order to add bituminous material to the receptacle thereby allowing the escape of large amounts of volatiles to the atmosphere.

It has been found that if the volatiles given oil? by the bituminous material in the heat liquification process are subjected to combustion, they will be converted into gaseous oxides, etc., having a reduced tendency to contaminate the atmosphere and which do not have an obnoxious odor. Thus, in the prior art, the removable cover 15 has been provided with an opening communicating with a chimney member. One or more burner devices supplied with liquid or gaseous fuel pressure have been mounted in such chimney members to provide a flame therein for the purpose of drawing off the volatiles from the receptacle and subjecting them to combustion within the chimney member prior to allowing them to escape into the atmosphere. This is obviously a wasteful solution to the problem and it has previously been suggested that such volatiles be drawn into the heating tubes in some way for combustion, so that the heat resulting therefrom would serve a useful purpose. However, the devices heretofore proposed have been ineflicient and have tended to provide a means by which combustion is propagated into the receptacle itself resulting in an explosive burning or blow-back, which is a name given to the uncontrolled burning of the volatiles and bituminous material in the kettle itself. Such blow-back may damage the kettle or overheat the bituminous material even if it is brought under control prior to causing injury to persons and property.

According to this invention, a means is provided for drawing off the volatiles from the receptacle and subjecting them to complete combustion within the heating tubes without danger of blow-back. As shown in FIGS. 1 and 2 a device 40 according to the teaching of this invention and which is referred to herein in its various embodiments as a vacuum collar or vacuum collar venturi is applied to the end of the portion 24 of the heating tube 18 adjacent the torch 30. It will be understood that the heating tubes 18 and torch 30 of a roofing kettle or the like for heating bituminous material are carefully designed with respect to each other to provide eflicient transfer of heat from the flame of the torch to the bituminous material, complete combustion of the flame within the heating tube 18 and maximum life of the heating tube 18 under operating conditions. The vacuum collar 40 according to the teachings of this invention not only maintains such design relationship between the torch 30 and the heating tube 18, but can improve such relationship.

As most clearly shown in FIGS. 2 and 3 a vacuum collar according to one embodiment of this invention suitable for use on existing kettles comprises a short tubular member 41 which is inserted coaxially into the heating tube 18 at the end thereof adjacent the torch 30. The major portion of the tubular member 41 has external dimensions which are smaller than the internal dimensions of the heating tube 18. However, the end of the tubular member 41 adjacent the torch 30 is flared outwardly to dimensions equivalent to the internal dimensions of the heating tube 18. According to the embodiment of this invention shown in FIGS. 2 and 3 the flared end of the tubular member 41 is provided with a return flange 42 which surrounds the body of the tubular member 41 and has internal and external dimensions corresponding to those of the heating tube 18 to thereby provide a short extension of such heating tube 18. Thus, when the free end of the flange 42 is butted against the end of the heating tube 18 the body of the tubular member 41 will project into the heating tube 18 and annular volume 43 opening into the heating tube 18 will be provided between the exterior of the tubular member 41 and the interior of the heating tube 18 and flange 42. The flange 42 is provided with an opening through the wall thereof and a ventpipe 44 communicating with such opening is mounted to extend into the space between the upper surface of the bituminous material 34 and the removable cover 15. As more fully described hereinafter when the flame of the torch 30 is directed into the heating tube 18 through the tubular member 14 it will be forced to constrict in passing through the tubular member 41 and subsequently expand within the heating tube 18 resulting in a zone of decreased gas pressure at the open end of the annular volume 43 between the exterior of the tubular member 41 and the interior of the heating tube 18 and flange 42. Such zone of reduced gas pressure will tend to create a partial vacuum within the annular volume 43 drawing volatiles from the surface of the bituminous material 34 through the vent pipe 44 into such annular volume 43 and out the open end thereof into the flame of the torch 30 within the heating tube 18. Due to the high velocity of the flame and gases at this particular point in the heating tube 18, it has been found that the flame does not tend to propagate into the an nular volume 43 thus reducing to a minimum the danger of the occurrence of a blow-back (i.e., propagation of the flame through the annular volume 43 and vent pipe 44 into the interior of the receptacle). Furthermore, it has been found that by proper dimensioning of the annular volume 43 and vent pipe 44 as well as tubuar member 41, the escape of volatiles from the receptacle other than through the vent pipe 44 can be eliminated. Finally, it has been found that not only does complete combustion of the volatiles occur within the heating tube 18, but that such combustion contributes significantly to the heating of the bituminous material thereby reducing the amount of fuel which must be supplied to the torch 30 in operation. An additional benefit of the vacuum collar 40 is that it tends to increase the life of the heating tube in operation as will be described more fully hereinafter.

Referring to FIG. 3 an exploded view of an embodiment of this invention suitable for use on existing kettles of the type described above is shown. It will be understood that a vacuum collar according to the teaching of this invention may be used with substantially all existing kettles regardless of their specific design. For example, as shown in FIG. 3, the torch 30' of certain ones of existing kettles may comprise a plurality of burners joined together as a unit. As shown in FIG. 3, three burner jets together with their associated burner shells each independently supplied with liquid or gaseous fuel under pressure through lines 31' may be combined into a single torch. However, the flame produced by such a multi-burner torch will have substantially the same characteristics insofar as this invention is concerned as a single burner torch. Thus, devices according to this invention are not limited to use with any particular kind of torch.

As also shown in FIG. 3, it has been found desirable for the vent pipe 44 to communicate with the annular volume 43 in an asymmetric fashion. To this end a vent pipe adapter 44' may be provided on the flange 42 in order to provide a transition from a circular vent pipe to an elongated oval or slot type opening in the flange 42. Such slot type opening in flange 42 is preferably not centered on the axis of the flange 42 in order to impart a helical swirling motion to the volatiles introduced into the annular volume 43 through vent pipe 44 and vent pipe adapter 44'. Such helical swirling action may be further enhanced by means of three or more spacer vanes 38 which may comprise appropriate elongated metallic blocks fixed at an appropriate angle to the exterior surface of the tubular member 41 as shown in FIG. 3. In addition to enhancing the swirling motion of the gases, such spacer vanes 38 also facilitate the insertion of the tubular member 41 into the heating tube portion 24 and serve to maintain the coaxial relationship therebetween during mounting and subsequent operation.

As shown in FIG. 3, a vacuum collar in accordance with the teachings of this invention may be mounted on the kettle by means of lugs 45 provided at the free end of flange 42, which lugs 45 are fastened to the end wall 12 of the kettle by means of screws 46. It has been found that the joint between the free end of the flange 42 and the end of the heating tube 18 need not be hermetic since the suction created by the low pressure Zone at the open end of the annular volume 43 is sufiicient to draw all of the volatiles from the receptacle through the vent pipe 44 even where there is a substantial leakage of air into the annular space 43 at the joint between the flange 42 and the heating pipe 18. It is of course desirable that the holes 47 which receive the screws 46 not penetrate the end wall 12 since this would tend to enable the leakage of liquid bituminous material from the re ceptacle unless appropriate gaskets are used. In many instances, the lugs 45 and screws 46 may be dispensed with and the free end of the flange 42 simply tack-welded to the heating tube 18 or end wall 12 as indicated in FIGS. 1 and 2.

It will be understood from the above description that the removable cover 15, burner well 17 and heating tubes 18 are fabricated as a single unit. The reason for this is two fold. In the first place the heating tubes tend to become coated with bituminous material in operation and must be removed for periodic cleaning. It will be understood that bituminous material in direct contact with the heating tubes tends to be heated to a higher temperature than the desired average temperature causing a coating of over-heated bituminous material to build up on and around the heating tube 18. If such coating is not removed periodically, it will build up to a point at which it will interfere with the eflicient. transfer of heat from the heating tube 18 to the bituminous material. In the second place, the heating tube 18 will tend to be eroded by the flame from the torch 30 during operation particularly if the torch 30 is not exactly aligned with the axis of the heating tube, thereby directing the flame against the side of the heating tube 18. It will be understood that torch 30 is adjustable within the burner well 17 so that the torch may be adjusted in its position with respect to the end of the heating tube 18 for optimum performance. However, after the kettle has been in use for a period of time, it is to be expected that maladjustmerits will occur from time to time and that, in any event, erosion of the heating tube 18 by the flame of the torch 30 suflicient to Weaken the heating tube will eventually occur for whatever reason. It then becomes necessary to replace the heating tube 18 or at least the portion thereof which has been weakened by erosion. This is usually done by cutting out the eroded portion of the heating tube and welding in a new section in its place. As would be expected, the erosion of the heating tube tends to be most severe at the entrance to the heating tube adjacent the torch 30. Thus, the vacuum collar according to the teaching of this invention provides the additional benefit of tending to protect the heating tube 18 from erosion by the flame of the torch 30. The vacuum collar itself will, of course, tend to be eroded by the flame of the torch 30, however, the vacuum collar may be replaced much more easily than a section of the heating tube. Furthermore, the tubular member 41 of the vacuum collar 48 will be cooled by the passage of gases through the annular volume 43 and thus will not tend to be eroded as quickly by the entering flame as would the end of the heating tube if no vacuum collar 40 were present.

Referring to FIG. 4, it will be seen that a vacuum collar 40' according to the teaching of this invention may be incorporated into kettles for heating masses of bituminous material as originally constructed without sacrificing any of the advantages discussed hereinabove. Thus, an oppropriate slot or opening 48 may be provided through the side Wall of the heating tube 18 and an appropriate vent pipe 44 or adaptor 44' may be welded liquid tight to the heating tube 18 in communication with the slot or opening 48. The vent pipe 44 of this embodiment will, of course, extend upwardly within the receptacle through the liquid bituminous material to a point above the surface of the liquid bituminous material within the receptacle. The flange 42 on the tubular member 41 may then be replaced by a simple mounting flange 42'. Thus the tubular member 41 will tend to protect the heating tube 18 from erosion due to the flame of the torch 30 and may be easily replaced when erosion of the tubular member 41 itself occurs.

Referring to FIG. 4, it will be understood that the heating tube 18 will have a circular cross-section of given diameter designated by the letter A. For optimum operation the flame produced by the torch 30 will likewise have a given diameter, designated by the letter A, smaller than but approaching the diameter A of the heating tube 18. Although the exact contour imparted to the flame of the torch 30 by the tubular member 41 in the heating tube 18 is not known, it is believed that it will tend to follow the dot-dash lines 49 shown in FIG. 4. As shown by such dotdash lines 49, the contour of the flame is believed to first expand, then constrict and then expand again as it leaves the torch 30 and passes through the tubular member 41 into the heating tube 18. It will be seen that such supposed contour is very similar to the contour of the internal surface of the well known venturi tube and it has been found that a low pressure gas region tends to occur at the end of the annular space formed between the tubular member 41 and the interior of the heating tube 18 perhaps for the same reason that reduced pressure occurs at the throat of a conventional venturi tube. In any event, it has been found that a tubular member 41 having a diameter, indicated by the letter B, which is between 60% and of the diameter A of the heating tube 18 will produce a sufliciently reduced pressure within the annular volume 43 to draw the volatiles from the receptacle through the vent pipe 44 and into the flame within the heating tube 18 without unduly reducing the efficiency of the torch and heating tube 18 in operation. If the diameter of the tubular member 41 is too small, it will, of course, interfere with the entrance of the flame of the torch 30 into the heating tube 18. On the other hand, if the diameter of the tubular member 41 is made too large, it will tend to reduce the venture effect provided by the tubular member 41 and unduly const-riot the annular volume 43 impeding the flow of volatiles there-through. It has been found that the cross-sectional area of the annular 'volume 43 should be about twice the cross-sectional area of the vent pipe 44 for optimum performance. It has also been found that the length of the tubular member, indicated by the letter C, should be between about 50% and about of the diameter A of the heating tube 18. If the length C is too small than the venturi eifect of the tubular member 41 is reduced and there is a greater danger of a blow-back due to combustion propagating through the annular volume 43 and vent pipe 44 into the receptacle. If, on the other hand, the length C is made too long, it will again reduce the venturi effect produced by the tubular member 41 and will also tend to interfere with the efl'iciency of the heat transfer from the flame of the torch 30 to the bituminous material through the heating tube 18.

It will be understood that the maximum velocity of the gases in the heating tube 18 occurs where the most violent combustion takes place, thus producing the maximum expansion of gases. As the gases proceed through the heating tube and heat is extracted therefrom through the heating tube 18 and into the bituminous material, the volume of the gases decreases resulting in a decrease in velocity thereof. Thus, there is an optimum diameter B and length C for the tubular member 41 for any given heating tube and torch arrangement. As shown in FIG. 5, the vacuum collar venturi according to the embodiment shown in FIG. 4 or any other embodiment of this invention may be provided with a plurality of vent pipes 44 or adaptors 44' communicating with the annular volume 43.

As shown in FIGS. 4 and 5, the tubular member 41 may have a wall thickness substantially the same as the wall thickness of the heating tube 18. If so, it is desirable to provide the free end of tubular member 41 with a knifeedge 39 due to the fact that volatiles in the gases drawn into the annular volume 43 may tend to deposit carbon on the exterior of the tubular member 41. Such knife-edge 39 will tend to operate at a high temperature and thus pre- 'vent the build up of carbon deposits at the boundary between the annular volume 43 and the flame which could tend to trigger combustion in such annular volume 43. It will be understood that the tubular member 41 could have a thinner wall thickness than the heating tube 18 due to the cooling of such tubular member 41 by gases passing through annular volume 43, which cooling will tend to reduce the erosion of the tubular member 41 by the flame.

Referring to FIGS. 6 through 8, it will be seen that a vacuum collar venturi according to the teaching of this invention is also applicable to the type of roofing kettle or the like which does not include a burner well 17. In this type of kettle, the heating tube 18' is removably mounted directly on the receptacle itself. Thus, as shown in FIG. 7, one end of the heating tube 18 is bolted to one end wall of the receptacle in registry with an opening through such'end wall and appropriate gaskets are used to prevent leakage of the liquid bituminous material 34 from the receptacle at the bolted joint. As shown in FIG. 6, the heating tube may make a single U-shaped passage within the receptacle terminating in an upwardly extending portion 27' which may be bolted or otherwise attached to a rigid upper wall portion of the receptacle. A cover portion 19' may be mounted on the receptacle by means of hinges 20' to facilitate access to the interior of the receptacle. As indicated in FIGS. 6 and 7, the liquid bituminous material 34 may be pumped out of the receptacle through an outlet pipe 51 by means of a motor 52 and pump 53 arrangement. As also shown in FIGS. 6- and 7, the receptacle may be mounted on wheels 54 by an appropriate spring means 55 and may be provided with an appropriate tongue structure 56 to enable the receptacle to be towed as a trailer. The torch 30 as well as the motor 52 for the pump 53 may be mounted on the tongue structure 56 together with an appropriate source of liquid or gaseous fuel under pressure (not shown) connected to the torch 30 by means of connecting line 31.

Referring to FIG. 8, it will be seen that an embodiment of the vacuum collar venturi according to the teaching of this invention similar to that shown in FIG. 3 may be applied to the kettle of FIGS. 6 and 7. Similarly, referring to FIG. 9, it will be seen that the kettle shown in FIGS. 6 and 7 may be modified to enable the use of an embodiment of the vacuum collar venturi according to the teaching of this invention similar to that shown in FIG. 4. As shown in FIG. 8, three or more spacer vanes 38' similar to those 38 shown in FIG. 3 but modified to provide a helical swirling of the flame as well as the gases passing through the annular volume 43 may be provided. Such Hues 38' may comprise metal strips slotted to fit on the free end of the tubular member 41 at an angle as shown. Such vanes 38 extend across the annular volume 43 into contact with the interior of the heating tube 18 to position the tubular member 41 in the heating tube and enhance the swirling motion of the gases passing through the annular space 43. Such vanes also extend into the interior of the tubular member 41 tending to impart a swirling motion to the flame which will not only enhance the mixing of gases passing through the annular space 43 with the flame, but will also tend to enhance the heat transfer from the flame and hot gases to the heating tube 18 as they proceed through the balance of the heating system. The use of vanes 38' is particularly desirable in heating systems where the heating tube 18 is of large diameter since they will tend to prevent laminar flow of the hot gases and will contribute significantly to the elficiency of the heating system.

It will be understood that no attempt has been made herein to disclose details of construction of roofing kettles or the like which are not necessary for an understanding of this invention. For example, referring to FIG. 8, the end, side and bottom wall of the receptable of such kettles may be double walls 12 with an insulating layer 57 therebetween in order to minimize heat loss through the walls of the kettle.

Similarly, it will be understood that various combinations may be made of the features of the different embodiments of this invention shown and described herein and that other modifications may be made in the embodiments of this invention disclosed herein without departing from the teaching of this invention. It is believed that those skilled in the art will adapt the teaching of this invention 10 to both the retrofitting and the original construction of a wide variety of heating devices in which a flame from a torch is directed into a heating tube for the purpose of heating materials which give off pollutants at elevated temperatures than can be rendered harmless by more complete combustion thereof.

What is claimed is:

1. A roofing kettle and the like for heating masses of bituminous material and the like comprising:

(a) a receptable, having a removable cover, for containing said material with a space between the surface of said material and said removable cover;

(b) a heating tube of given internal dimensions within said receptacle and having a portion extending within said receptacle, both ends of said heating tube being adapted to extend into communication with the surrounding atmosphere;

(c) a torch unit adapted to direct a flame into one end of said heating tube, said torch unit and said heating tube being designed and arranged with respect to each other to cause said flame to communicate the desired heat to said material with the products of combustion of said flame exiting from the other end of said heating tube;

(d) a tubular member received within said heating tube at said one end thereof, one end of said tubular member being flared outwardly to external dimensions which are substantially equal to said given internal dimension of said heating tube adjacent said one end of said heating tube, the remainder of said tubular member having smaller external dimensions than said given internal dimensions of said heating tube and extending substantially co-axially Within said heating tube from said flared end of said tubular member to form a substantially annular volume therebetween open to the interior of said heating tube at the free end of said tubular member;

(e) means mounting the periphery of said flared end of said tubular member at said one end of said heating tube; and

(f) a vent pipe communicating between said annular volume formed between said tubular member and said heating tube and said space between said surface of said material in said receptacle and said removable cover of said receptacle.

2. A roofing kettle and the like as claimed in claim 1 wherein said means mounting the periphery of said flared end of said tubular member comprises a tubular return flange extending from said periphery and surrounding the body of said tubular member in spaced relation thereto, the free end of said flange being mechanically mounted at said one end of said heating tube and said vent pipe communicates with said annular volume through an opening in said flange.

3. A roofing kettle and the like as claimed in claim 1 wherein said means mounting the periphery of said flared end of said tubular member comprises a planar flange extending outwardly from said periphery transversely of the axis of said tubular member, said planar flange being mechanically mounted at said one end of said heating tube and said vent pipe communicates with said annular volume through an opening in said heating tube.

4. A roofing kettle and the like as claimed in claim 1 wherein said means mounting the periphery of said tubular member at said one end of said heating tube includes a welded joint.

5. A roofing kettle and the like as claimed in claim 1, wherein said free end of said tubular member is provided with a knife edge.

6. A roofing kettle and the like as claimed in claim 1, wherein said vent pipe communicates with said annular volume through an opening in said heating tube and extends through said material in said receptacle into communication with said space between the surface of said material and the removable cover of said receptacle.

7. A roofing kettle and the like as claimed in claim 1 wherein said vent pipe communicates with said annular volume asymmetrically with respect to the axis of said tubular member whereby gases entering said annular volume from said vent pipe are urged to follow a helical path within said annular volume.

8. A roofing kettle and the like as claimed in claim 1 wherein more than one vent pipe communicates between said annular volume and said space.

9. A roofing kettle and the like as claimed in claim 1, wherein a spacer vane extends between the inner surface of said heating tube and the outer surface of said tubular member.

10. A roofing kettle and the like as claimed in claim 1 wherein a plurality of vanes spaced from each other about the periphery of said tubular member and each comprising a slotted metallic sheet are mounted at the end of said tubular member with a first portion thereof extending References Cited UNITED STATES PATENTS 2,496,113 1/1950 Wollner 126343.5 A 3,046,977 7/1962 Figge 126343.5 A 3,220,403 11/1965 Figge 126343.5 A

WILLIAM F. ODEA, Primary Examiner P. D. FERGUSON, Assistant Examiner US. Cl. X.R. 

